Plasma ion source and charged particle beam apparatus

ABSTRACT

A plasma ion source includes: a gas introduction chamber, into which raw gas is introduced; a plasma generation chamber connected to the gas introduction chamber and made of a dielectric material; a coil wound along an outer circumference of the plasma generation chamber and to which high-frequency power is applied; an envelope surrounding the gas introduction chamber, the plasma generation chamber and the coil; and insulating liquid filled inside the gas introduction chamber, the plasma generation chamber and the envelope to immerse the coil and having an dielectric strength voltage relatively greater than that of the envelope and the same dielectric dissipation factor as the plasma generation chamber.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Japanese Patent Application No.2015-026843, filed on Feb. 13, 2015, the entire subject matter of whichis incorporated herein by reference.

BACKGROUND

1. Field of the Invention

The present disclosure relates to a plasma ion source and a chargedparticle beam apparatus.

2. Description of the Related Art

Conventionally, a configuration for a plasma ion source is known, inwhich a flow restrictor is provided for restricting flow of gasintroduced into a plasma chamber to generate voltage drop between a gassupplier and plasma in gas maintained at high pressure so as to suppressarc discharge (for example, JP-A-2011-142081).

In the plasma ion source of the related art, a cooling fluid channel isprovided around a plasma generation chamber in order to cool a wallportion of a plasma generation chamber, the temperature of which easilyincreases due to contact with high-density plasma, and a coil which iseasily heated by applying high-frequency power. Therefore, the entiresize of the plasma ion source increases to several times that of theplasma generation chamber.

SUMMARY

The present disclosure has been made in view of such a problem and oneof objects of the present disclosure is to provide a plasma ion sourceand a charged particle beam apparatus, which are capable of preventingthe entire size of the plasma ion source from increasing in order toensure desired cooling performance.

According to an exemplary embodiment of the present disclosure, there isprovided a plasma ion source including: a gas introduction chamber, intowhich raw gas is introduced; a plasma generation chamber connected tothe gas introduction chamber and made of a dielectric material; a coilwound along an outer circumference of the plasma generation chamber andto which high-frequency power is applied; an envelope surrounding thegas introduction chamber, the plasma generation chamber and the coil;and insulating liquid filled inside the gas introduction chamber, theplasma generation chamber and the envelope to immerse the coil andhaving an dielectric strength voltage relatively greater than that ofthe envelope and the same dielectric dissipation factor as the plasmageneration chamber.

According to another exemplary embodiment of the present disclosure,there is provided a charged particle beam apparatus including: theplasma ion source; an ion beam barrel that irradiates ion beam by ionsof the raw gas generated in the plasma ion source; a stage on which asample is mounted; and a controller that controls the ion beam barreland the stage to irradiate the ion beam onto the sample and performs atleast any one of observation, processing and analysis of an irradiatedarea of the sample.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects of the present disclosure will become moreapparent and more readily appreciated from the following description ofillustrative embodiments of the present disclosure taken in conjunctionwith the attached drawings, in which:

FIG. 1 is a schematic cross-sectional view showing the configuration ofa charged particle beam apparatus according to an embodiment of thepresent disclosure;

FIG. 2 is a schematic cross-sectional view showing the configuration ofa plasma ion source according to an embodiment of the presentdisclosure;

FIG. 3 is a plan view showing an insulation member of a plasma ionsource according to an embodiment of the present disclosure when viewedfrom a plasma generation chamber side; and

FIG. 4 is a cross-sectional view of an insulation member and a terminalelectrode taken along a IV-IV line shown in FIG. 3.

DETAILED DESCRIPTION

Hereinafter, a plasma ion source and a charged particle beam apparatusaccording to an embodiment of the present disclosure will be describedwith reference to the accompanying drawings.

A charged particle beam apparatus 10 according to the present embodimentincludes a sample chamber 11, the inside of which is able to maintain ina vacuum state, a stage 12 for fixing a sample S in the sample chamber11, and an actuator 13 that actuates the stage 12, as shown in FIG. 1.The charged particle beam apparatus 10 includes a focused ion beam lensbarrel 14 for irradiating focused ion beams FIB to an irradiated subjectin a predetermined irradiation area (that is, a scan range) in thesample chamber 11. The charged particle beam apparatus 10 includes anelectron beam barrel 15 for irradiating electron beams EB to theirradiated subject in the predetermined irradiation area in the samplechamber 11. The charged particle beam apparatus 10 includes a detector16 for detecting secondary charged particles (secondary electrons orsecondary ions) R generated from the irradiated subject by irradiationof the focused ion beams or electron beams. The charged particle beamapparatus 10 includes a detector (not shown) for detecting secondarycharged particles (reflection electrons) generated from the irradiatedsubject by irradiation of electron beams in the electron beam barrel 15.The charged particle beam apparatus 10 includes a gas supply unit 17 forsupplying gas Ga to a surface of the irradiated subject. The chargedparticle beam apparatus 10 includes a display device 20 for displayingimage data based on secondary charged particles detected by the detector16, a controller 21 and an input device 22.

The charged particle beam apparatus 10 may perform various processes(etching process, etc.) through sputtering and form a deposition film byscanning and irradiating the focused ion beams onto the surface of theirradiated subject. The charged particle beam apparatus 10 may perform aprocess of forming, in the sample S, a cross section for cross-sectionobservation through a scanning-type electron microscope and a process offorming a sample piece (for example, a thin sample, a needle-shapedsample, etc.) for transmission observation through a transmission-typeelectron microscope. The charged particle beam apparatus 10 may scan andirradiate the focused ion beams or electron beams onto the surface ofthe irradiated subject such as the sample S, thereby observing thesurface of the irradiated surface.

The sample chamber 11 is evacuated until the inside thereof becomes adesired vacuum state by an exhaust device (not shown) and is configuredto maintain a desired vacuum state. The stage 12 holds the sample S.

The actuator 13 is housed in the sample chamber 11 in a state of beingconnected to the stage 12 and displaces the stage 12 with respect to apredetermined axis according to a control signal output from thecontroller 21. The actuator 13 includes a movement mechanism 13 a formoving the stage 12 in parallel along X and Y axes parallel to ahorizontal plane and orthogonal to each other and a Z axis of a verticaldirection orthogonal to the X and Y axes. The actuator 13 includes atilt mechanism 13 b for tilting the stage 12 around the X axis or Y axisand a rotation mechanism 13 c for rotating the stage 12 around the Zaxis.

The focused ion beam lens barrel 14 is fixed to the sample chamber 11such that a beam emission unit (not shown) faces the stage 12 at a upperside of the stage 12 in a vertical direction within the irradiation areain the sample chamber 11 and an optical axis thereof is parallel to thevertical direction. Thus, focused ion beams can be irradiated to theirradiated subject such as the sample S fixed on the stage 12 downwardin the vertical direction.

The focused ion beam barrel 14 includes a plasma ion source 14 a forgenerating ions and an ion optical system 14 b for focusing anddeflecting the ions emitted from the plasma ion source 14 a. The plasmaion source 14 a and the ion optical system 14 b are controlled accordingto a control signal output from the controller 21 and the irradiationposition and irradiation condition of the focused ion beam is controlledby the controller 21. The ion optical system 14 b includes a firstelectrostatic lens, such as a condenser lens an electrostatic deflector,a second electrostatic lens such as an objective lens and the like, forexample. Although two sets of electrostatic lenses are shown in FIG. 1,three sets or more of electrostatic lenses may be provided. In thiscase, an aperture is mounted between the lenses in the ion opticalsystem 14 b.

The plasma ion source 14 a is a high-frequency inductively-coupledplasma ion source. The plasma ion source 14 a includes a torch 30, firstground potential flange 31 and second ground potential flange 32, a gasintroduction chamber 33, a plasma generation chamber 34, a gasintroduction chamber material 35, a terminal electrode 36, a plasmaelectrode 37, an insulation member 38, a coil 39, an envelope 40 andinsulating liquid 41, as shown in FIG. 2.

The torch 30 has a tube shape. The torch 30 is made of a dielectricmaterial. The dielectric material may be any one of quartz glass,alumina and aluminum nitride, for example. In a first end of the torch30, the first ground potential flange 31 is provided. In a second end ofthe torch 30, the second ground potential flange 32 is provided. Thefirst ground potential flange 31 and the second ground potential flange32 are maintained at a ground potential. The first ground potentialflange 31 and the second ground potential flange 32 are made ofnon-magnetic metal such as copper or aluminum, for example.

The torch 30 provides chambers that serve as the gas introductionchamber 33 and the plasma generation chamber 34. The gas introductionchamber 33 is formed by the gas introduction chamber material 35connected to the first ground potential flange 31 and the terminalelectrode 36 provided in the torch 30. The plasma generation chamber 34is formed by the terminal electrode 36 and the plasma electrode 37provided at the second end of the torch 30. The terminal electrode 36and the plasma electrode 37 are made of non-magnetic metal such ascopper, tungsten, and molybdenum. Since plasma is attached to the innerwall of the torch 30 by sputtering the terminal electrode 36 and theplasma electrode 37, tungsten or molybdenum having high energy necessaryfor sputtering is preferable. The insulation member 38 is housed in thegas introduction chamber 33. The coil 39 wound along the outercircumference of the plasma generation chamber 34 is provided outsidethe torch 30. High-frequency power is supplied from an RF power source39 a to the coil 39.

The envelope 40 is connected to the first ground potential flange 31 andthe second ground potential flange 32 so as to surround the gasintroduction chamber 33, the plasma generation chamber 34 and the coil39. The insulation liquid 41 in which the coil 39 is immersed betweenthe gas introduction chamber 33 and the plasma generation chamber 34 andthe envelop 40.

In the gas introduction chamber material 35, an opening 35 a forintroducing raw gas supplied from a gas supply source (not shown) via aflow controller (not shown) into the gas introduction chamber 33 isformed.

In the terminal electrode 36 provided at the boundary between the gasintroduction chamber 33 and the plasma generation chamber 34, aplurality of through-holes 36 a for introducing raw gas from the gasintroduction chamber 33 to the plasma generation chamber 34 is formed.The size of each of the plurality of through-holes 36 a (for example,the diameter of the circular through-hole 36 a) is smaller than thelength of a plasma sheath. The length of the plasma sheath is severaltens of micrometer to several hundreds of micrometer, for example.

In the plasma electrode 37, an opening 37 a for extracting ions out fromthe plasma generation chamber 34 is formed.

The insulation member 38 of the gas introduction chamber 33 is fixed tothe terminal electrode 36 by a connection member (not shown) such as abolt. As shown in FIG. 3, a mounting hole 38 a, in which a connectionmember is mounted, is formed in the insulation member 38. In an oppositesurface 38A of the insulation member 38 facing a surface 36A of theinsulation electrode 36, as shown in FIG. 4, a concave groove 38 b isformed. The depth D of the concave groove 38 b is smaller than thelength of the plasma sheath. The width W of the concave groove 38 b isgreater than the depth D. In the insulation member 38, a plurality ofthrough-holes 38 c formed in the concave groove 38 b is formed. The sizeof each of the plurality of through-holes 38 c (for example, thediameter of the circular through-hole 38 c) is smaller than the lengthof the plasma sheath. The size of each of the plurality of through-holes38 c is equal to the size R of each of the plurality of through-holes 36a in the plasma electrode 37, for example. Each of the plurality ofthrough-holes 38 c is located to face each of the plurality ofthrough-holes 36 a in the plasma electrode 37, for example.

In addition, in the plasma electrode 37, a mounting hole 36 b, in whichthe connection member (not shown) is mounted, is formed to face themounting hole 38 a of the insulation member 38.

The insulation member 38 is shaped to prevent direct movement of chargedparticles between the gas introduction chamber material 35 and theterminal electrode 36. The insulation member 38 is shaped such that thegas introduction chamber material 35 and the terminal electrode 36 arenot directly visible to the other. The insulation member 38 has a malethread shape, for example.

The envelope 40 is made of a material having a high heat dissipationproperty (thermal conductivity) such as copper or aluminum, for example.

The insulating liquid 41 has a dielectric strength voltage relativelygreater than that of the envelope 40 and the same dielectric dissipationfactor as the plasma generation chamber 34. The insulating liquid 41 isfluorine based inert liquid.

The electron beam barrel 15 is fixed to the sample chamber 11 such thata beam emission unit (not shown) faces the stage 12 in an inclinationdirection inclined at a predetermined angle from the vertical directionof the stage 12 within the irradiation area in the sample chamber 11 andan optical axis thereof is parallel to the inclination direction. Thus,the electron beams may be irradiated to the irradiated subject such asthe sample S fixed on the stage 12 downward in the inclinationdirection.

The electron beam barrel 15 includes an electron source 15 a forgenerating electrons and an electronic optical system 15 b for focusingand deflecting the electrons emitted from the electron source 15 a. Theelectron source 15 a and the electronic optical system 15 b arecontrolled according to a control signal output from the controller 21and the irradiation position and irradiation condition of the electronbeams are controlled by the controller 21. The electronic optical system15 b includes, for example, an electromagnetic lens and a deflector.

The electron beam barrel 15 and the focused ion beam barrel 14 may beexchangeably arranged, such that the electron beam barrel 15 is arrangedin the vertical direction and the focused ion beam barrel 14 is arrangedin the inclination direction inclined at the predetermined angle fromthe vertical direction.

The detector 16 detects the intensity of secondary charged particles(secondary electrons, secondary ions, and the like) R (that is, theamount of secondary charged particles) radiated from the irradiatedsubject when the focused ion beams or the electron beams are irradiatedto the irradiated subject such as the sample S and outputs informationon the amount of detected secondary charged particles R. The detector 16is located at a position where the amount of secondary charged particlesR is capable of being detected in the sample chamber 11, for example, atan oblique upper side of the irradiated subject such as the sample Swithin the irradiated area, and is fixed to the sample chamber 11.

The gas supply unit 17 is fixed to the sample chamber 11 such that a gasspraying unit (not shown) faces the stage 12 in the sample chamber 11.The gas supply unit 17 may supply, to the sample S, etching gas forselectively facilitating etching of the sample S by the focused ionbeams according to the material of the sample S, deposition gas forforming a deposition film by a deposited material such as metal orinsulator on the surface of the sample S, and the like. For example,etching gas such as xenon fluoride for an Si based sample S, water forthe sample S of an organic system, or the like is supplied to the sampleS while irradiating the focused ion beams, thereby selectivelyfacilitating etching. For example, deposition gas of compound gascontaining phenanthrene, platinum, carbon, tungsten or the like issupplied to the sample S while irradiating the focused ion beams,thereby depositing a solid component decomposed from the deposition gason the surface of the sample S.

The controller 21 is arranged outside the sample chamber 11 and isconnected to the display device 20 and the input device 22 foroutputting a signal according to input operation of an operator, such asa mouse and a keyboard.

The controller 21 integrally controls operation of the charged particlebeam apparatus 10 by a signal output from the input device 22 or asignal generated by a predetermined automatic operation control process.

The controller 21 converts the amount of secondary charged particlesdetected by the detector 16 while scanning the irradiation position ofthe charged particle beam into a luminance signal corresponding to theirradiation position and generates image data indicating the shape ofthe irradiated subject by two-dimensional position distribution of theamount of detected secondary charged particles. The controller 21displays a screen for executing operation such as enlargement, reductionand rotation of each image data on the display device 20 along with eachgenerated image data. The controller 21 displays a screen for performinga variety of settings such as processing settings on the display device20.

As described above, according to the plasma ion source 14 a of theembodiment of the present disclosure, since the plasma generationchamber 34 and the coil 39 can be cooled by the insulating liquid 41filled in the envelope 40, it is possible to prevent the entire size ofthe plasma ion source 14 a from increasing as compared to the case ofproviding the insulating liquid channel such as a heat pipe around theplasma generation chamber 34 and the coil 39, for example.

Since the coil 39 is arranged as close as possible to the plasmageneration chamber 34 in the envelope 40, it is possible to efficientlyapply high-frequency power to plasma.

Since the envelope 40 is made of a material having high thermalconductivity, heat delivered from the plasma generation chamber 34 andthe coil 39 to the envelope 40 by convection of the insulating liquid 41is efficiently dissipated from the envelope 40.

Since the envelope 40 is made of non-magnetic metal having high electricconductivity, it is possible to prevent useless power loss fromincreasing even when induction current is generated around the coil 39.

As described above, according to the charged particle beam apparatus 10of the embodiment of the present disclosure, it is possible to preventthe entire size of the apparatus from increasing.

In the above-described embodiment, a heat dissipation fin may beprovided in the envelope 40.

In the above-described embodiment, a device (a cooling device, a pumpand the like) for pumping the insulating liquid 41 out of the envelope40 and supplying the insulating liquid into the envelope 40 aftercooling may be provided.

In the above-described embodiment, the electron beam barrel 15 may beomitted.

In the above-described embodiment, the controller 21 may be a softwarefunctional unit or a hardware functional unit such as LSI.

What is claimed is:
 1. A plasma ion source comprising: a gasintroduction chamber, into which raw gas is introduced; a plasmageneration chamber connected to the gas introduction chamber and made ofa dielectric material; a coil wound along an outer circumference of theplasma generation chamber and to which high-frequency power is applied;an envelope surrounding the gas introduction chamber, the plasmageneration chamber and the coil; and insulating liquid filled inside thegas introduction chamber, the plasma generation chamber and the envelopeto immerse the coil and having an dielectric strength voltage relativelygreater than that of the envelope and the same dielectric dissipationfactor as the plasma generation chamber.
 2. The plasma ion sourceaccording to claim 1, wherein the envelope is made of copper oraluminum.
 3. The plasma ion source according to claim 1, wherein theinsulating liquid is fluorine based inert liquid.
 4. The plasma ionsource according to claim 1, wherein the plasma generation chamber ismade of any one of quartz glass, alumina and aluminum nitride.
 5. Theplasma ion source according to claim 1 further comprising: a heatdissipation fin provided in the envelope.
 6. A charged particle beamapparatus comprising: the plasma ion source according to claim 1; an ionbeam barrel that irradiates ion beam by ions of the raw gas generated inthe plasma ion source; a stage on which a sample is mounted; and acontroller that controls the ion beam barrel and the stage to irradiatethe ion beam onto the sample and performs at least any one ofobservation, processing and analysis of an irradiated area of thesample.
 7. The charged particle beam apparatus according to claim 6further comprising: an electron beam barrel that irradiates electronbeam, wherein the controller further controls the ion beam barrel andthe electron beam barrel to irradiate the ion beam and the electron beamonto the same area of the sample and performs at least any one ofobservation, processing and analysis of the irradiated area of thesample.